The data communications industry has progressively used more and a greater variety of sizes of equipment. Certain equipment is typically mounted on a relay rack. The industry has adopted a standard (ANSI/TIA/EIA-310E, "Cabinets, Racks, Panels and Associated Equipment") for relay racks. The most widely used relay rack in this standard is the "19-inch" relay rack. It has an equipment opening of seventeen and three-quarters inches between the mounting posts. Although the width of the equipment is specified in the '310E standard, the depth is not. The industry utilizes equipment, such as electronic hubs and routers, which can be heavy and have a variety of depths. Typically this heavy and deep equipment has been mounted in cabinets, which have two parallel sets of mounting posts of the standard width so the equipment can be secured on all four corners. The problem is the depth of a given cabinet is fixed and the depth of the equipment is not. It follows that a dual relay rack which has an adjustable depth is desirable, but the width of a relay rack should be the established uniform width. The installation of a dual relay rack for receiving equipment of a variety of depths should be effected by a single workman to provide an economical installation of the relay racks.